This invention relates to a method of manufacturing micro-electronic devices including a selectively positioned diamond film. More particularly, this invention is directed to the manufacture of an emission array having a diamond film deposited onto the field emission tips.
The method of the invention is particularly well suited to be used in the manufacture of a Spindt-type cathode including a diamond film on the field emission tips for use in field emission displays. Throughout the specification, numerous references will be made to the use of the inventive method in the manufacture of Spindt-type field emission arrays, however, it should be realized that the inventive method could be used in any instance wherein a diamond film is being deposited on a micro-electronic device.
A reason for the focus on field emission displays is provided by an article by Katherine Derbyshire entitled "Beyond AMLCDs: Field Emission Displays", appearing in Solid State Technology, 37 (11) November, 1994, wherein the author states that the flat panel display market is growing even more rapidly than display makers have expected. It is stated that in the not too distant future, personal digital assistants, virtual reality driven robotics, global positioning systems, and many other civil and military applications will depend on portable, efficient, high-performance displays to communicate with users. Field emission displays are believed to represent one mechanism with which to achieve such advances.
Furthermore, televisions and cathode ray tubes (CRTs) presently utilize a thermionic cathode to produce a primary electron beam directed onto a phosphorous screen to create an image. These cathodes produce electrons when heated sufficiently for thermionic emission and an image is produced by rastering the electron beam across the view screen. Larger screen diameters require a larger cathode-to-screen distance to enable the electron beam to cover the entire screen, which results in a very cumbersome package, reduced beam density and ultimately a darker display. In addition, thermionic cathode technology is rapidly approaching the brightness limit due to the physical properties in the materials used. Therefore, the increased commercial and military demand for higher resolution and larger viewing area televisions and data collection monitors cannot be met with current display technology.
However, field emission cold cathodes which operate on the principle of electron emission due to a high applied electric field at the emitter tip, may offer a solution to the above-described commercial demand. In fact, early microfield emission devices were produced by Spindt in 1968. The shortfalls of a Spindt-type cathode are low output intensity and relatively high applied electric field corresponding to high voltage required for electron emission.
It has been recognized that diamond provides unique properties to a field emission display. Particularly, diamond film has been observed to produce stable electron emission at relatively low applied fields. Also, diamond is a robust material well known for its high chemical and temperature resistance. In fact, field emitters coated with polycrystalline diamond have demonstrated very high emission currents, a low effective work function, a large effective emission rate and high current stability. For example, in an article entitled "Microstructure and Field Emission of Diamond Particles on Silicon Tips" by E. L. Givargizov et al. in Applied Surface Science, 87/88 (1995) 24-30, it was concluded that polycrystalline diamond coated silicon whiskers demonstrate large emission currents. In addition, Givargizov, in an article entitled "Silicon Tips With Diamond Particles on them: New Field Emitters?" Journal of Vacuum Science and Technology, 13 Mar./Apr., 1995, stated that silicon tips with high aspect ratios on which diamond particles were deposited by a hot filament process demonstrated operability as a field emission cathode. More particularly, the emitters were prepared on the butt-ends of silicon rods, having conical plateau ends about 200 microns in diameter where silicon whiskers were grown, sharpened, and diamond particles deposited on their ends. From each of the samples, all tips were removed except one having a spherical diamond particle on the very end about one micron in diameter.
In an article by Hong et al. entitled "Field Emission from p-type Polycrystalline Diamond Films", Journal of Vacuum Science and Technology, 13 Mar./Apr., 1995, it is disclosed that diamond film deposited by chemical vapor deposition (CVD) on field emitter substrates yielded field emissions at electric field intensity less than 20 MV/m. In this disclosure, a hot-filament CVD (HFCVD) system was employed to fabricate the polycrystalline diamond emitter structures. Particularly, a filament temperature of 2300.degree. C. in an atmosphere of 1% CH.sub.4 in H.sub.2 50 Torr was used to achieve a diamond deposition rate of approximately 0.25 .mu.m hr. and a final film thickness of 2 .mu.m. In addition, a container of pure boron powder was placed in the substrate holder for in situ doping of diamond film.
Similarly, Liu, et al. in an article entitled "Field Emission Characteristics of Diamond Coated Silicon Field Emitters", Journal of Vacuum Science and Technology, 13 Mar./Apr. 1995, demonstrated that single crystal silicon field emitters modified to include a surface deposition of diamond from bias-enhanced microwave plasma chemical vapor deposition exhibited significant enhancement both in total emission current and stability compared to pure silicon emitters. Moreover the effective work function of the polycrystalline diamond coated emitter surfaces was found to be larger than that of a pure silicon emitter surface.
However, none of the above-described procedures are able to achieve reproducible uniform growth of diamond crystallites on all emitter cones of a Spindt-type emission array.